1. Field of the Invention
The present invention relates in general to a device for determining stalk strength of crop plants and, more specifically, to a stalk tension measuring device which is calibrated, preferably spring loaded, and equipped to measure tension without breaking the stalks tested.
2. Description of the Prior Art
It is known in the art to use devices to assist in determining stalk strength and moisture levels in plants. Such information can be used to help determine readiness of the plants for harvest or to simply examine and compare the stalk strength of plants.
U.S. Pat. No. 4,954,783 discloses a corn moisture tester, which operates by enclosing an ear of corn in a close-able sleeve. Upon closure of said sleeve around the ear of corn, conductor blades or electrodes pierce the kernels and the electrical conductivity is measured. This conductivity provides a measure of the moisture in the kernels but does not allow testing of moisture or strength of stalks.
A device for testing the strength of plant stalks is disclosed by U.S. Pat. No. 5,044,210. Here, the device includes a frame with an upright member attached to a spring loaded horizontal arm secured to a moving vehicle. As the vehicle moves along a row of plants, the arm engages each plant. If the plant is strong enough it will bend and not break or the arm will pivot rearwardly on its way past the stalk and then spring back to its position before engaging the next plant. If it is not strong enough, the stalk will break. A measurement of the strength of the group of stalks is obtained by counting the number of broken stalks in the row.
Of course, tension can be measured in other ways. Although other devices have been disclosed for measuring tension in general, such as weighing scales, the disclosures of these devices do not contemplate their use for measuring tension in plant stalks nor would these devices be aperable for that purpose. For example, U.S. Pat. No. 570,553 granted in 1896 discloses a portable weighing scale which includes a hollow handle in telescopic relationship with a tube. One end of the tube is attached to a spring in the handle, the other to a scoop positioned above the handle. The weight of material placed in the scoop can be taken by reading the position of the tube against a graduated scale as said tube is pushed downward into the handle by the weight of the material. However, this device would not work for stalk strength measurements because it is not designed to be hand-held, or used horizontally or to press, but not break, stalks of a given strength.
Other simple weighing scales have been patented that disclose devices against which is hung the item to be weighed, rather than weighing the item by placing it on or above the scales. Examples include U.S. Pat. Nos. 855,754; 3,223,189; 1,141,562; 2,570,321; 4,785,897. Most of these include a first member in telescopic or slidable relationship with another. Said first member is then associated with the item to be weighed such that the weight of the item acts to move the first member against a tension element. The relative position of the first member is then compared to its resting position to obtain a measure of the weight of the item.
None of the above-mentioned devices provide a device which allows measurement of the strength of plant stalks. What was needed was a device that can be used to measure stalk strength in the field on vertically growing stalks without breaking the stalks, by a conveniently hand-held device, and in a way that is calibrated such that measurements can be compared across time and location. Such a device would provide a way for a researcher or farmer to compare the stalk strengths of different varieties or cultivars, at various stages in the growing season. If recorded, such data could be used to evaluate the stalk characteristics of these plants in various climates, geographic locations, moisture patterns, and fertilizer or herbicide/pesticide applications.
The present invention provides a light weight, hand-held device. This device can be calibrated to meet standards such that even if multiple devices are used by multiple people in multiple places, measurements so taken will be consistent and have meaning. In addition, the present invention can be provided with differing tension elements and in sizes adapted to the size and general strength expected for the stalks of a given crop. Finally, the present invention is designed to be simply and effectively used in the field on growing plants and with a minimum of stalk breakage.